The present invention relates to the field of electrical connectors, and, more particularly, to an electrical connector and associated manufacturing method.
Underground and submersible junction bus connectors are widely used in electrical power distribution systems. One type of such connector is offered under the designation SWEETHEART(copyright) by Homac Mfg. Company of Ormond Beach, Fla., the assignee of the present invention. The SWEETHEART(copyright) connector is a cast or welded aluminum connector including a bus, or bar, portion and a series of tubular posts extending outwardly from the bus portion. The posts have an upper open end to receive one or more electrical conductors. A threaded bore is provided in the sidewall of the post, and which receives a fastener to secure the electrical conductor within the upper end of the post. An insulating coating is provided on the lower portion of the posts and bus of the connector. In addition, EPDM insulating sleeves may be used to provide waterproof seals for the posts.
Unfortunately, the casting method for making such a connector may result in small trapped bubbles which leave internal voids in the casting. The internal voids may reduce the strength of the connector. The surface texture of the cast parts may be relatively rough, thereby requiring additional grinding or finishing steps. In addition, different molds are typically required for the different connector sizes and configurations. Accordingly, casting may be relatively expensive. In addition, a cast part may have a lower electrical conductivity.
U.S. Pat. Nos. 5,766,044; 5,555,620 and 5,608,965 each discloses an alternate approach to casting of the bus and post connector. A hollow-end milling cutter is used to form the entire extent of the upstanding posts from generally rectangular extruded stock material, and while also leaving the bus or bar portion at the base of the connector. In other words, an integrally formed monolithic connector is produced without casting and starting from extruded aluminum stock.
While the hollow-end milling approach offers a number of potential advantages, there are also shortcomings. In particular, a relatively large amount of the starting aluminum stock material must be removed and is therefore wasted. Also, the cost of the aluminum stock may also be relatively high because the stock must have a height dimension that is at least as great as the bus portion plus the full height of the posts. Of course, the number of required machining steps may increase the cost of the electrical connector produced by such hollow-milling cutter techniques.
In view of the foregoing background, it is therefore an object of the present invention to provide a method for making a bus and post connector preferably without casting, and while reducing the waste and other drawbacks of the hollow-milling cutter based approaches of the prior art.
This and other objects, features and advantages in accordance with the present invention are provided by a method for making an electrical connector by engaging respective locking pins into respective lower open ends of the posts and extending outwardly and into corresponding openings in the bus to secure the posts and bus together with the posts extending outwardly from the bus. Engaging the locking posts to the bus may also comprise expanding each locking pin radially outwardly to securely engage adjacent portions of the bus and post. Accordingly, strong mechanical and electrical connection is established between the bus and the posts.
Expanding each locking pin outwardly may comprise impacting at least one end face of the locking pin. More particularly, in some embodiments, each post further has an upper open end in communication with the lower open end to define a bore extending through the post. Thus, expanding each locking pin outwardly may comprise positioning a first forming tool into the bore to contact a first end face of the locking pin, and while positioning a second forming tool on an opposite side of the bus to contact a second end face of the locking pin opposite the first end face.
At least one opening in the bus and the lower open end of a corresponding post may have a substantially similar cross-sectional shape. The cross-sectional shape may be generally circular and uniform, and, therefore, a corresponding locking pin may have a cylindrical shape.
In other embodiments, at least one opening in the bus may have a generally circular cross-sectional shape and the open lower end of a corresponding post may have a tapered circular cross-sectional shape. For these embodiments, the corresponding locking pin has a cylindrical lower portion for the opening in the bus, and a frustoconical upper portion for the tapered open lower end of the corresponding post. This taper angle may in a range of about 1-5 degrees, for example.
The posts may also have different configurations. For example, at least one post may further have an upper open end in communication with the open lower end to define a bore through the post for receiving at least one electrical conductor. In addition, such a post may have at least one threaded passageway extending transversely into the bore. In addition, the post may have an increased thickness wall portion through which the at least one threaded passageway extends. This provides greater holding strength for the associated fastener. In other embodiments, one or more of the posts may have a closed upper end and an uppermost tab with at least one opening therein for receiving a fastener to secure an electrical conductor thereto.
The method may also include forming an insulating coating on at least the bus and lower portions of the posts. The bus may have a generally rectangular shape. In addition, at least one or all of the bus, posts and locking pins preferably comprises a metal, such as aluminum, for example. Extruded aluminum may be particularly advantageous and avoids some of the drawbacks of cast aluminum, for example. In some embodiments, the electrical connector may include posts having different configurations or sizes, as to accommodate different sized conductors.
Another aspect of the invention relates to the electrical connector, such as formed by the above described method. More particularly, the electrical connector may include a bus having a plurality of openings therein; a plurality of posts for connecting to electrical conductors, each post having a lower open end; and a plurality of locking pins, each locking pin extending from within a respective lower open end of a post into a corresponding opening in the bus to connect the posts and bus together so that the posts extend outwardly from the bus. At least one opening in the bus and the lower open end of a corresponding post may have a substantially similar cross-sectional shape. This cross-sectional shape may be generally circular and uniform, and the corresponding locking pin will also have a cylindrical shape.
At least one opening in the bus may also have a generally circular cross-sectional shape, and the lower open end of a corresponding post may have a tapered circular cross-sectional shape. For these embodiments, the corresponding locking pin preferably has a cylindrical lower portion for the opening in the bus and a frustoconical upper portion for the lower open end of the corresponding post. The frustoconical upper portion may have a taper angle in a range of about 1-5 degrees.
The upper end of one or more of the posts may be open and in communication with the open lower end to receive an electrical conductor. Alternately, the upper end of the post may have a tab with an opening therein to receive a fastener for securing an electrical conductor to the post.